Average Weather in July in Tamalpais-Homestead Valley California, United States

For reference, on September 11, the hottest day of the year, temperatures in Tamalpais-Homestead Valley typically range from 55°F to 72°F, while on January 1, the coldest day of the year, they range from 43°F to 54°F.

The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on July. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Clouds

The month of July in Tamalpais-Homestead Valley experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 11% throughout the month. The lowest chance of overcast or mostly cloudy conditions is 8% on July 20.

The clearest day of the month is July 20, with clear, mostly clear, or partly cloudy conditions 92% of the time.

For reference, on January 11, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 55%, while on July 20, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 92%.

The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Tamalpais-Homestead Valley, the chance of a wet day over the course of July is essentially constant, remaining around 1% throughout.

For reference, the year's highest daily chance of a wet day is 31% on February 20, and its lowest chance is -0% on July 25.

The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during July in Tamalpais-Homestead Valley is essentially constant, remaining about 0.0 inches throughout, and rarely exceeding 0.2 inches or falling below -0.0 inches.

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Sun

Over the course of July in Tamalpais-Homestead Valley, the length of the day is decreasing. From the start to the end of the month, the length of the day decreases by 37 minutes, implying an average daily decrease of 1 minute, 15 seconds, and weekly decrease of 8 minutes, 45 seconds.

The shortest day of the month is July 31, with 14 hours, 7 minutes of daylight and the longest day is July 1, with 14 hours, 45 minutes of daylight.

The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise of the month in Tamalpais-Homestead Valley is 5:51 AM on July 1 and the latest sunrise is 21 minutes later at 6:12 AM on July 31.

The latest sunset is 8:36 PM on July 1 and the earliest sunset is 16 minutes earlier at 8:19 PM on July 31.

Daylight saving time is observed in Tamalpais-Homestead Valley during 2018, but it neither starts nor ends during July, so the entire month is in daylight saving time.

For reference, on June 21, the longest day of the year, the Sun rises at 5:48 AM and sets 14 hours, 48 minutes later, at 8:35 PM, while on December 21, the shortest day of the year, it rises at 7:22 AM and sets 9 hours, 32 minutes later, at 4:54 PM.

The solar day over the course of July. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

Humidity

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy in Tamalpais-Homestead Valley is essentially constant during July, remaining around 0% throughout.

For reference, on September 12, the muggiest day of the year, there are muggy conditions 0% of the time, while on January 1, the least muggy day of the year, there are muggy conditions 0% of the time.

The percentage of time spent at various humidity comfort levels, categorized by dew point.

Wind

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Tamalpais-Homestead Valley is gradually decreasing during July, decreasing from 8.9 miles per hour to 8.1 miles per hour over the course of the month.

For reference, on May 30, the windiest day of the year, the daily average wind speed is 9.5 miles per hour, while on October 21, the calmest day of the year, the daily average wind speed is 7.2 miles per hour.

The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

Tamalpais-Homestead Valley is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average surface water temperature in Tamalpais-Homestead Valley is gradually increasing during July, rising by 2°F, from 54°F to 56°F, over the course of the month.

The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Growing Season

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

Temperatures in Tamalpais-Homestead Valley are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.

Time Spent in Various Temperature Bands and the Growing Season in July

The percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days in Tamalpais-Homestead Valley are increasing during July, increasing by 325°F, from 1,028°F to 1,353°F, over the course of the month.

The average growing degree days accumulated over the course of July, with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy in Tamalpais-Homestead Valley is essentially constant during July, remaining within 0.2 kWh of 8.2 kWh throughout.

The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

For the purposes of this report, the geographical coordinates of Tamalpais-Homestead Valley are 37.878 deg latitude, -122.536 deg longitude, and 230 ft elevation.

The topography within 2 miles of Tamalpais-Homestead Valley contains very significant variations in elevation, with a maximum elevation change of 1,024 feet and an average elevation above sea level of 306 feet. Within 10 miles contains very significant variations in elevation (2,569 feet). Within 50 miles contains large variations in elevation (3,789 feet).

The area within 2 miles of Tamalpais-Homestead Valley is covered by artificial surfaces (37%), shrubs (24%), trees (21%), and herbaceous vegetation (10%), within 10 miles by water (52%) and artificial surfaces (19%), and within 50 miles by water (45%) and grassland (18%).

Data Sources

This report illustrates the typical weather in Tamalpais-Homestead Valley year round, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

There are 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Tamalpais-Homestead Valley.

The estimated value at Tamalpais-Homestead Valley is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Tamalpais-Homestead Valley and a given station.

Other Data

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.